Multiple hydrocyclone system

ABSTRACT

A centrifugal pump has a housing containing a plurality of pump rotors spaced along a common rotation axis and also containing layers of cyclones in the spaces between adjacent rotors, the cyclones of each layer being disposed radially in a circle or ring concentric to the rotation axis and with their narrow ends directed toward this axis and provided with an outlet, each cyclone having an inlet at its wide end portion. The cyclones of one layer have their inlets connected to the pressure side of a pump rotor and have their outlets connected to the suction side of a pump rotor, whereby the cyclone layers are connected in series so as to effect progressive concentration of a sludge contained in a suspension.

United States Patent [72] Inventor Bengt lngrnar Dahlberg Tumba, Sweden [21] Appl. No. 876,803

[22] Filed [45] Patented Nov. 14, 1969 Feb. 2, 1971 [7 3] Assignee Alfa-Laval AB Tumba, Sweden a corporation of Sweden [32] Priority Nov. 15, 1968 [3 3 Sweden [3 l 15514/68 [54] MULTIPLE HYDROCYCLONE SYSTEM Primary Examiner.l. L. Decesare Attorney-Davis, Hoxie. Faithfull and Hapgood ABSTRACT: A centrifugal pump has a housing containing a plurality of pump rotors spaced along a common rotation axis and also containing layers of cyclones in the spaces between adjacent rotors, the cyclones of each layer being disposed radially in a circle or ring concentric to the rotation axis and with their narrow ends directed toward this axis and provided with an outlet, each cyclone having an inlet at its wide end portion. The cyclones of one layer have their inlets connected to the pressure side of a pump rotor and have their outlets connected to the suction side of a pump rotor, whereby the cyclone layers are connected in series so as to effect progressive concentration ofa sludge contained in a suspension.

MULTIPLE HYDROCYCLONE SYSTEM THE DISCLOSURE The present invention relates to a multiple hydrocyclone system of the type having cyclones located in the housing of a centrifugal pump and arranged in a ring or circle concentric to the axis of rotation of the pump. Such a cyclone system is known in the art and is disclosed, for example, in the Swedish Pat. No. 166,096. This cyclone system, however, allows a separation in only one stage; and the same is true of the cyclone system according to Swedish Pat. No. 181,191. An object of the present invention is to provide a multiple hydrocyclone system of the above-described type which enables a separation in a plurality of stages while utilizing a compact arrangement, and which eliminates pipelines and pumps connected between the different stages of conventional multiple stage systems.

In a system according to the invention, the housing of the centrifugal pump contains a plurality of pump rotors spaced along a common rotation axis; and in the spaces between adjacent rotors are layers of cyclones, the cyclones of each layer being disposed radially of the aforesaid axis with their narrow ends directed toward the axis and provided with outlets from the respective cyclones. The wide end portions of the cyclones are provided with inlets; and the inlets of the cyclones of one layer are connected to the pressure side of a pump rotor, while the outlets from the narrow ends of the cyclones in a layer open at the suction side of a pump rotor.

An arrangement of this kind makes it possible, by means of cyclone layers connected in series to each other, to concen- -trate in successive stages a sludge contained in a suspension.

One example of this is the production of a starch concentrate from a starch suspension. However, it is desirable in separating a suspension to free the sludge concentrate from soluble and insoluble impurities. This is also the case when separating a starch suspension, in that it is desired to remove gluten, fine fibers and soluble proteins from the starch concentrate by means of washing with water. A special arrangement of the invention, intended for countercurrent washing, is characterized in that outlets from the wide ends of the cyclones in a layer are connected to the suction side of that rotor which feeds, the cyclones in an adjacent layer.

According to an additional feature of the invention, the pump rotors can be vaneless in the region of the inlets of the cyclones. Thus, the latter are fed without pulsation effects generated by the rotors, which effects would have a disturbing influence on the separation course in the cyclones.

The invention is described more in detail in the following, reference being had to the accompanying drawings, in which:

FIG. I is a flow diagram of a preferred form of the new cyclone system as illustrated in FIGS. 2 and 3;

FIG. 2 is an axial sectional view of a portion of the preferred form, the parts on one side of the axis being omitted; and

FIG. 3 is a side elevational view of the preferred form.

The invention as illustrated will be described in connection with the separation of a starch suspension in water, although it is not limited thereto.

Referring to FIG. 1, each of the cyclones shown at 1, 2 and 3 represents only one of the cyclones in a corresponding layer of cyclones located between a pair of adjacent pump rotors, the cyclones in each layer being arranged in a circle or ring concentric to the axis of the rotors, as previously described. Four rotors of the centrifugal pump are indicated at 4, 5, 6 and 7, these rotors being spaced axially along a common pump shaft (not, shown) to provide the three interrotor spaces for the three cyclone layers 1, 2 and 3. The pump rotors 5, 6 and 7 feed the cyclones 1, 2 and 3 through channels 8, 9 and 10, respectively. The inlet into the cyclone system for the starch suspension to be separated is designated at 11 and the outlet for washed starch concentrate is designated at 12. Washing water is supplied to the suction side of the pump rotor 5 through an inlet 13 and dilutes starch concentrate coming from the cyclone 2 and then being separated in the cyclone 1.

This washing water is then led in countercurrent to the starch suspension through the cyclones by means of the channels 14 and 15 and discharges finally, together with suspension water, through an outlet 16.

As shown in FIG. 2, a motor-driven shaft 17 drives the pump rotors, three of which are indicated at 18. Each pump rotor 18 feeds a layer of cyclones, one cyclone in each layer being shown at 19 and two such cyclones being shown in FIG. 2. Each cyclone is provided at its wide end portion with a tangential inlet 20 shaped as a guide vane, so that the pumping effect is kept low. The pump housing comprises stationary discs 21 of which two are shown in FIG. 2. These discs are provided at their peripheries with radially directed holes in which the cyclones 19 are inserted, and the outer ends of these holes are closed by plugs 22 provided with cyclone outlets 23 from the wide end portions of the cyclones. The cyclones have additional outlets 24 for starch concentrate, these outlets being at the narrow ends of the cyclones and being directed toward the shaft or rotation axis 17.

The pump housing also includes discs 25 inserted between the discs 21. The discs 21 and 25 have recesses extending radially in the direction towards the pump shaft 17 and for stiffening are provided with radial vanes 26 and 27 arranged in these recesses. Thus, these vanes form radial channels leading towards the suction side 18a of the pump rotors. The cyclone outlets 24 open into the radial channels formed by the vanes 26; and channels 28 leading from the outlets 23 open into the radial channels formed by the vanes 27. The pump rotors 18 have radial vanes 29 which terminate in edges 30, so that each rotor 18 has a vaneless region 31 which opens toward the inlet 20 of each cyclone in a layer of cyclones. Due to the low pressure prevailing at the center of the pump, labyrinth sealings 32 are sufficient to seal between the inner edge of the discs 21 and the pump rotors 18.

In FIG. 3, 33 designates an electric motor which drives the pump shaft 17. As appears at the right in FIG. 3, the multiple hydrocyclone system proper is formed by the discs 21 which, by means of bolts 34 and 35, are kept clamped together between two end walls 36 and 37 and in that way form a housing which is supported by a frame 38.

In the operation of the illustrated system, the starch suspension to be separated and washed is fed to the pump rotor 18 located farthest to the right and is pumped radially outward to the vaneless space 31 opening toward the inlet 20 of each cyclone 19 in the adjacent layer of cyclones. This feeding of the suspension to the extreme right-hand rotor 18 is effected through the inlet 11 (FIG. 1) which delivers the suspension to the rotors suction side 18a by way of a suitable passage (not shown) in the pump housing. In the vaneless space 31, which forms the pressure side of the pump rotor, the pulsations generated by the pump rotor vanes 29 are smoothed out so that the starch suspension enters each cyclone as a uniform flow. The water being separated off is discharged from the system through the corresponding cyclone outlet 23 and channel 28, while the starch concentrate leaves the corresponding cyclone outlet 24 and is fed by the next pump rotor 18 to each cyclone 19 in the next (to the left) layer of cyclones, until the concentrate, having been washed clean, leaves the last layer of cyclones (situated farthest to the left) in the system. Pure washing water is led into the system through the channel 28, situated farthest to the left, and dilutes the starch concentrate which leaves the outlet 24 of each cyclone 19 in the layer situated farthest but one to the left. This water is then separated off in the cyclones situated farthest to the left and passes through their outlets 23 and the corresponding channels 28 to the inlets of the next cyclones, calculated in the direction to the right, until it is fed into the cyclones situated farthest to the right. Thus, a washing in countercurrent to the starch concentrate leaving the cyclone system has been effected.

As will be seen from the preceding, the present cyclone system requires only one motor and pump, common to all separation stages, and forms a compact design which requires little space and can be assembled completely in a factory. In

spite of the fact that the cyclone system according to the invention operates with a plurality of separation stages, the provision of special pipelines and insertion of special pumps between the different separation stages is avoided. In this way, the manufacturing and assembling costs for the system are reduced. and furthermore the energy losses owing to flow resistance in the pipeline channels will be small.

lclaim:

l. in a multiple hydrocyclone system, the combination of a centrifugal pump including a housing and a plurality of pump rotors disposed in the housing and adapted to be driven about a common axis, said rotors being spaced from each other along said axis and each having a suction side and a pressure side located, respectively, at a relatively small radius and a relatively large radius from said axis, and layers of cyclones disposed in the housing in the spaces between adjacent rotors and with the cyclones of each layer arranged in a ring concentric to said axis, each cyclone extending radially of said axis and having its narrow end directed toward said axis and provided with an outlet, each cyclone also having an inlet at its wide end portion, the cyclones of one layer having their said inlets connected to said pressure side of a pump rotor and having their said outlets located at said suction side of a pump rotor.

2. The combination according to claim 1, especially adapted for countercurrent washing, in which said wide end portions of the cyclones of one layer are provided with outlets connected to said suction side of that rotor which, through its said pressure side, feeds said inlets of the cyclones in an adjacent layer.

3. The combination according to claim 1, in which said pump rotors are vaneless in the regions of said inlets of the cyclones. 

1. In a multiple hydrocyclone system, the combination of a centrifugal pump including a housing and a plurality of pump rotors disposed in the housing and adapted to be driven about a common axis, said rotors being spaced from each other along said axis and each having a suction side and a pressure side located, respectively, at a relatively small radius and a relatively large radius from said axis, and layers of cyclones disposed in the housing in the spaces between adjacent rotors and with the cyclones of each layer arranged in a ring concentric to said axis, each cyclone extending radially of said axis and having its narrow end directed toward said axis and provided with an outlet, each cyclone also having an inlet at its wide end portion, the cyclones of one layer having their said inlets connected to said pressure side of a pump rotor and having their said outlets located at said suction side of a pump rotor.
 2. The combination according to claim 1, especially adapted for countercurrent washing, in which said wide end portions of the cyclones of one layer are provided with outlets connected to said suction side of that rotor which, through its said pressure side, feeds said inlets of the cyclones in an adjacent layer.
 3. The combination according to claim 1, in which said pump rotors are vaneless in the regions of said inlets of the cyclones. 